Hi, I'm the one in the video. I've had this comment a few times, with CRTs, no way. Your face would probably be 8 inches away from the front tube to fill your peripheral vision and you wouldn't be able to focus on it without getting fatigue for long.

It is possible it was meant for a CAVE VR room projection system, but I think the more likely answer (as there is no rear view) is that it was just a limitation of the engine. There is no system in Doom for rendering only part of the 2D screen offset from the main view (you cannot pan to look up or down as an example). Doom's FOV was 90 degrees for a single view, so they likely just rotated the drone views 90 degrees to render the "adjacent" area of the screen.